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New features

CSS and JS code coverage

Find unused CSS and JS code with the new Coverage tab. When you load or
run a page, the tab tells you how much code was used, versus how much was
loaded. You can reduce the size of your pages by only shipping the code
that you need.

Figure 1. The Coverage tab

Clicking on a URL reveals that file in the Sources panel with a breakdown
of which lines of code executed.

Figure 2. A breakdown of code coverage in the Sources panel

Each line of code is color-coded:

Solid green means that line of code executed.

Solid red means it did not execute.

A line of code that is both red and green, such as line 3 in Figure 2,
means that only some code on that line executed. For example, a ternary
expression like var b = (a > 0) ? a : 0 is colored both red and green.

Full-page screenshots

Check out the video below to learn how to take a screenshot from the top
of the page, all the way to the bottom.

Block requests

Want to see how your page behaves when a particular script, stylesheet, or
other resource isn't available? Right-click on the request in the Network
panel and select Block Request URL. A new Request blocking tab
pops up in the Drawer, which lets you manage blocked requests.

Figure 3. Block Request URL

Step over async await

Up until now, trying to step through code like the snippet below was a
headache. You'd be in the middle of test(), stepping over a line, and then
you'd get interrupted by the setInterval() code. Now, when you step through
async code like test(), DevTools steps from the first to last line with
consistency.

Changes

Unified Command Menu

When you open the Command Menu now, notice that your command
is prepended with a greater-than character (>). This is because the Command
Menu has been unified with the Open File menu, which is
Command+O (Mac), or Control+O
(Windows, Linux).

Discover other DevTools features

Below is a list of everything that's been covered in the What's New In DevTools series.